1. Field of the Invention
The invention concerns a device for applying adhesive to a workpiece, the device including a nozzle head that can be supplied with viscous adhesive under pressure and an application nozzle, wherein the nozzle head and the workpiece are moveable relative to each other via robotic means, such that the adhesive emitted from the application nozzle, preferably in the manner of a spray jet, is applied to the workpiece in the form of an adhesive strip along a predefined line of application. In the following the term “adhesive” is intended to include other viscous materials, such as insulation, which can be applied to a workpiece in viscous form via an application nozzle.
2. Description of the Related Art
In the application of adhesives it is known to apply a viscous adhesive, with or without air manipulation, onto the workpiece in the form of an adhesive strip along an application line. It is further known to deflect and swirl a thread of adhesive emitted from an application nozzle according to the whirlwind principle with the aid of compressed gas and in this manner to apply upon the workpiece a strip-like, partially open, strip of material of defined breadth (EP 0576498 B1). With this type of application it has also been taken into consideration, the recognition that depending upon the viscosity or stiffness of the adhesive material, a more or less viscous or tenacious adhesive thread is emitted, even though the flow amount of material out of the application nozzle of the nozzle head remains the same and that, one on the other hand, depending upon the viscosity or tenacity of this thread, a greater or lesser gas stream is required in order to deflect the thread in predefined manner and to produce a defined strip breadth. For this, a parameter which depends upon the viscosity of the pasty material is measured, and the amount of compressed gas supplied for the time interval is so controlled in functional dependence upon the measured viscosity parameter, such that a material strip of constant breadth is sprayed along the workpiece. As viscosity dependent parameter one could consider the extrusion pressure of the material, the temperature of the pasty material and the drive pressure or, as the case may be, the drive output of a dispensing or dosing device for the pasty material. In the case that the compressed gas supply is made viscosity dependent, this involves a control technical measure which requires a substantial calibration effort. Above all in the case of the change of application parameters, in the case of changing the robot program or in the case of changing the adhesive or the workpiece surface, recalibrations are necessary, which can be quite time consuming.